Mazda 3 Rear brakes/rotor? rattle over bumps, only quiet when I brake.

I bought a used 2008 mazda 3i manual trans with just under 60k miles on it. It was great in the beginning but I was worried about some grinding noise when braking and the rear rotors being a little worn down and rusty from sitting. Took it in for an oil change a little less than a month into having the car and had them look at the brakes while I was there, they wanted me to get a complete brake job. Don't know if there is any correlation to the noise and the shop visit/brake inspection but... turns out I don't really trust these new guys that took over this shop that I used to normally go to --- shortly after that visit is when I first started hearing the awful clunking noise coming from the rear.

I've asked many people's opinions/educated guess but they all say it could be loose links, suspension, sway bar, struts... etc etc. but I am not convinced it's any of those.

Whenever I go over even the slightest bump I can hear the loud clank of metal on metal coming from the rear, on both sides. I'm convinced it's my rotor or something to do with the brake pads... As soon as I step on the brake, the noise is silenced no matter how hard the bump or how rough the road. And as soon as I start to let up on the brake, the noise comes back. It's just awful and embarrasing to drive anywhere... :[

--Hoping a brake job would fix the problem, I took it in for new brakes and rotors to a family friend. It was quiet for a few miles and it (although much more of a mild clank at first) came back and became louder pretty quickly..


I took the wheel off to look around and see if I could poke around to hear any loose parts and tap around but couldn't find anything. Finally, I did notice that the rotor moves back and forth (or side to side?).. So, if I were on the side of the car to be able to look at the rotor head on, the rotor can easily be moved/pulled back and forth towards me. Is it supposed to do that? I tested the movement on my front rotors and those don't budge (and also don't rattle). HELP!

My first independently purchased car... and I'm embarrassed to drive it because the clanking and clunking is so loud..

 

when the wheel is bolted onto the car, it should be squezing the rotor in place and it should not move AT ALL.
Its possible there's corrosion around the center of the wheel so it isn't being tightened down properly. You can pull off a wheel and see if it goes on / off smoothly. Though that should be sort of obvious when someone is doing a brake job - figured he'd have seen something.

BTW, was the brake job pads or rotors too?

 

Thanks for the post/suggestion! So the last 2 places I've taken my car to couldn't figure it out. I took it to Excite Unlimited Motorsports in Westerville and they actually took the time to check a few resources - found the problem! The last shop that did my brake/rotor job put my brake pads on reversed (inner pads on the outside and outer pads on the inside)..... doi!

So I took it home, simply switched em around, and voila! No more noise Hooray!!! =D